Tuesday, September 07, 2010

FV-107 fixed crystal frequency

...Today it rained!

You may ask what that has to do with amateur radio...well first I don't recall last time I saw rain, probably in July, second it means the temperature will drop a little bit and it will be possible for me to do some soldering in the shack! That's the importance of rain...and of course I can stop watering my coriander plantation, the rain will do that for me :)

Continuing, as you probably know I have an FV-107, it's an external VFO for the FT-107 Yaesu transceiver but it's being used (connected) in my FT-102 with an adaptation circuit I made, the schematic and article available somewhere in this blog: (http://speakyssb.blogspot.com/2009/09/external-vfo-controller-for-ft-102.html)

The FV-107 VFO has provision for 6 fixed crystal operation. For crystal value selection you need to know your operation frequency, get a table provided by Yaesu (taking in account IF frequency scheme) make some calc's and then you have the VFO or crystal frequency, alternately you can put the radio in the frequency you want and measure the VFO output frequency, not very elegant solution....

Since I want to calc several frequencies and it's a repetitive boring task I made a small PHP online program that gives me instantly the needed crystal frequency and made it available for everyone to use, here's an usage example:
In the above example the frequency (f=) is 14200Khz and the mode (m=) is USB. The result VFO crystal will be 5248.5Khz. It can calculate for LSB/USB,AM and CW modes (use lsb our usb or amcw in the parameters), AM and CW have the same carrier frequency. 10m band isn't inserted in the programed frequency table just because it wasn't provided in the manual and I didn't use it. 17m band wasn't also in the manual but I calculated the IF values for the band.

Unfortunately it's difficult to find crystals in the range 5-5.5Mhz so for now my VFO will stay working as a true VFO :)

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